1. Field of the Invention
The present invention relates to an LED package, more particularly, which can more efficiently radiate heat generated from an LED chip.
2. Description of the Related Art
In general, a Light Emitting Diode (LED) package is required to have high light efficiency together with excellent heat radiating characteristics. In particular, since a high power LED package used in the lighting industry generates a large amount heat, its heat radiating performance is a critical factor to maintain the reliability of a device.
In view of such heat radiating characteristics, conventional LED packages incorporate a heat sink of high heat conductivity installed in a package substrate. As another approach, it is also considered to make a package substrate itself from a high heat conductivity material. Conventional LED package structures are shown in FIGS. 1(a) and 1(b).
Referring to FIG. 1(a), a conventional LED package 10 includes a package substrate 11 with an LED chip 15 mounted thereon by an adhesive layer 14. The package substrate 11 has a heat sink 11a acting as heat radiating (or conducting) means, extending in a thickness direction from a mounting area where the chip 15 is arranged. An upper substrate 12 arranged on the package substrate 11 has a cavity surrounding the mounting area. First and Second electrodes (not shown) of the LED chip 15 are connected, respectively, to first and second conductive leads 16a and 16b arranged on the package substrate 11.
In the LED package 10 shown in FIG. 1(a), heat generated from the LED chip 15 can be transferred to the heat sink 11a. In this case, as indicated by arrow C, the heat transfer path is limited to a vertical direction along the heat sink formed in the thickness direction.
Referring to FIG. 1(b), a conventional LED package 20 includes a package substrate 21 with an LED chip 25 mounted thereon by an adhesive layer 24. An upper substrate 22 arranged on the package substrate 21 has a cavity surrounding a chip-mounting area. First and second electrodes (not shown) of the LED chip 25 are connected, respectively, to first and second conductive leads 26a and 26b arranged on the package substrate 21.
The package substrate 21 is a semiconductor substrate such as a ceramic substrate or Si substrate which has high heat conductivity. Thus the package substrate 21 itself can act as a heat sink or heat radiating means. However, even though the package substrate itself acts as the heat sink, heat is transferred radially from a contact surface of the LED chip, that is, a heat source. Accordingly, most heat is transferred vertically along a path indicated by arrow C1 but little heat is transferred laterally.
As shown in FIG. 1(a) and 1(b), in a convention LED package, heat generated from an LED chip is transferred substantially vertically through a bonding area of the LED chip with a heat sink or a heat sink substrate. As a result, although the heat sink or heat sink substrate is larger than the area of the LED chip, most heat is transferred along a path formed in a thickness direction of the substrate.
Accordingly, in the convention LED packages, even though a large sized heat sink or a heat sink substrate is used, the area functioning as a heat transfer path is limited and thus excellent heat radiating performance is rarely expectable.